The second off-target,ballistic Soyuz landing in a row raises a troubling prospect for the future ofAmericans in space aboard the International Space Station.

When the shuttle programshuts down in 2010, the U.S. will rely on the Russians to deliver crews to thespace station. But if NASA deems the Soyuz spacecraft unreliable or dangerous,there is nothing to replace it for U.S. astronaut travel to the space station.

On Saturday, a Soyuzcapsule carrying NASA's Peggy Whitson, cosmonaut Yuri Malenchenko and SouthKorea spaceflight participant, So-Yeon Yi, had a technical problem and fellto Earth like a rock, landing some 260 miles off course. The landing cameafter a steeper-than normal re-entry caused the crew to endure dangerous forcesup to 10 times that of gravity, twice the normal re-entry pressure.

No cause is apparent, andteams from NASA and the Russian space agency have yet to begin investigatingthe cause of the apparent re-entry system failure.

"It's going to takeseveral days for them to get (the capsule) back to Moscow," said NASAspokesman Nicole Cloutier. "It does have a flight recorder."

A Soyuz spacecraftautomatically makes a ballistic re-entry if its guidance systems fails.Cosmonaut Yuri Malenchenko confirmed that the craft automatically made theswitch to the emergency re-entry system, but he could not say why.

"There was no actionof the crew that led to this," Malenchenko said. "Time will tell whatwent wrong."

Though tough on the crew, aballistic re-entry is relatively safe, said U.S. space station program managerMike Suffredini. A similar re-entry affected the lastSoyuz return in October 2007, which carried two cosmonauts and a Malaysianspace tourist.

The cause could be easilyfound after an examination of the capsule's flight recorder.

"Of course, if it'srelated to the last problem, that'll add data," Suffredini said.

The Russians immediatelypromised an investigation. And so far there has been no talk of grounding theSoyuz fleet.

"It's still afunctional spacecraft. The incidents don't rise to the level of requiring astand down," said James Oberg, an authority on the Russian and Chineselaunch systems and consultant for NBC News.

The Russians are preparingto increase their launch rate from two per year to four per year to provide fora six-person crew on the expanded space station in 2009. Oberg questionedwhether the production increase is somehow contributing to more problems.

"Has doubling theproduction overstressed their production safety and quality?" he asked.

A ballistic landing alsooccurred on May 3, 2003. The most recent ballistic landing was in October2007.

These incidents, coupledwith a cabin leak on re-entry in October 2005, raise questions about the Soyuz'otherwise long reputation for reliability. A total failure of the Soyuz onSaturday would have been tragic on many levels.

The spacecraft carried belovedU.S. astronaut Whitson, the first woman station commander and holder of theU.S. record for the most time in space. The craft also carried reveredcosmonaut Yuri Malenchenko, who has spent more than 500 days in space, and a SouthKorea spaceflight participant, whose $20 million trip was paid for by theSouth Korean government.

Aside from the loss oflife, if a fatal flaw developed in the Soyuz spacecraft, the U.S. and Russiawould have no other way to bring crews to and from the space station.

And if the Soyuz programwere grounded, the shuttle program could not be extended beyond 2010, when NASAwill divert its funding to the Constellation program -- a capsule designed togo the space station, to the moon and on to Mars.

Substantial fundingincreases would be necessary to revive the shuttle, a proposal neitherPresident Bush nor any of the three presidential contenders supports.

"We have the parts weneed on hand, with adequate spares to fly the manifest that's ahead of us, thenext 11 flights," Hale said last week. "But beyond that, if you wantto restart production (of the shuttle), you are probably too late."